OBJECT:
Hidden
A
Hidden object provides a text object on a form that is
hidden from the user and is created with every instance of an HTML <INPUT>
tag with the type attribute set to 'hidden'. A Hidden object is
used to pass name/value pairs when the form is submitted. These objects
are then stored in the elements array of the parent form and accessed
using either the name defined within the HTML tag or an integer (with
'0' being the first element defined, in source order, in the specified
form).

The following example creates a button that, when clicked, displays the
Hidden object's value in an alert box.